Biliary excretion of nitrazepam and its metabolites in rats

: A single intravenous administration of nitrasepam (10 mg/kg) resulted in its excretion as free and conjugated metabolites in the bile of albino rats. The initial compounds, amino- and acetamido derivatives were deteced among free metabolits. Conjugated forms were recovered as N-glucoronides (5-nitro-2-aminobenzophenon and amine) and as O-glucoronides (C3-hydroxylated derivatives of nitrasepam and of acetamide). The presence of a considerable amount of nitrasepam and of its metabolites in the rats' bile is suggestive of their enterohepatic circulation.